Brightening of polyacrylonitrile wet tow

ABSTRACT

The invention relates to a process for optically brightening polyacrylonitrile fibres, which have been manufactured by the wet spinning process and are in the gel state by means of selected types of anionic optical brightening agents.

nited States Patent [191 Eigenmann et al.

[451 Nov. 19, 1974 BRIGHTENING OF POLYACRYLONITRILE WET TOW Inventors: Gottfried Eigenmann, Therwil; Leo

Kaiser, Aesch; Christian Luethi, Muenchenstein, all of Switzerland Assignee: Ciba-Geigy AG, Basel, Switzerland Filed: June 8, 1972 Appl. No.: 260,786

Foreign Application Priority Data June 18, 1971 Switzerland 8929/71 US. Cl 117/7, 8/115.6, l17/33.5 R, 117/33.5 T, 252/30l.2 W, 260/240 CA, 260/240 B Int. Cl. C091) 23/14, C09k 1/60 Field of Search l17/33.5 T, 33.5 R, 7; 252/3012 W; 8/115.6; 260/240 CA, 240 B References Cited UNITED STATES PATENTS 8/1958 Long et al. 252/3012 W Blankenship et al. 8/1 15.6

Primary ExaminerWilliam D. Martin Assistant Examiner-William R. Trenor Attorney, Agent, or Firm-Joseph G. Kolodny; Edward McC. Roberts; Prabodh I. Almaula [5 7 ABSTRACT The invention relates to a process for optically brightening polyacrylonitrile fibres, which have been manufactured by the wet spinning process and are in the gel state by means of selected types of anionic optical brightening agents.

9 Claims, N0 Drawings BRIGHTENING OF POLYACRYLONITRILE WET TOW The present invention relates to a process for brightening optionally modified polyacrylonitrile fibres, which have been manufactured by the wet spinning process and are in the gel state, by means of selected types of compounds,

These types of compounds correspond to the formulae as" R wherein B denotes 4,4 -biphenylene, 1,4-phenylene or 2,6-naphthylene, R denotes hydrogen, alkyl with 1 to 4 carbon atoms, halogen, SO M or alkoxy with 1 to 4 carbon atoms located in the orthoor meta-position to the bridge member and M denotes a hydrogen, alkali metal, ammonium or amine salt ion, the solubility of these compounds in water at 90C being at least 10 g/l, preferably at least 40 g/l,

wherein X denotes hydrogen or halogen and A denotes a phenyl radical which is optionally substituted by alkyl with l to 4 carbon atoms, halogen or a SO M grouping (with M a hydrogen, alkali metal, ammonium or amine salt ion) and M denotes a hydrogen, alkali metal, ammonium or amine salt ion,

Lora OH= l. souvr s'oavr I I wherein X denotes hydrogen or halogen and A denotes a phenyl radical which is optionally substituted by alkyl with l to 4 carbon atoms, halogen or a -SO M grouping and M denotes a hydrogen, alkali metal, ammonium or amine salt ion and Z H Y wherein Y denotes hydrogen, alkyl with l to 4 carbon atoms or phenyl, Z and 2, independently of one another denote hydrogen or chlorine, M denotes a hydrogen, alkali mctal, ammonium or amine salt ion and n represents 1 r 2.

Within the framework of the formula (I), the compounds of the formula wherein R represents hydrogen, alkyl with l to 4 carbon atoms, halogen or alkoxy with l to 4 carbon atoms located in the orthoor meta-position to the bridge member and M denotes a hydrogen, alkali metal, ammonium or amine salt ion, should be particularly singled out.

As an example of a compound of the formula (2) there may be mentioned the compound of the formula and an eitample of a compound of the formula (3) there may be mentioned the compound of the formula in M N Q E N S OaNa whilstthe compounds of the formulae are embraced by the general formula (4).

According to the invention, the brighteners of the formulae (1 to are applied to the fibre manufactured by the wet spinning process whilst the fibre is still in the gel state. In the gel state, the fibre still contains large amounts of water and is therefore strongly swollen. After the fibre formation (spinning process) and the washing process for removing solvents or solubilising agents, the fibre is stretched to orient the macro-molecules and is subsequently dried. This causes the gel state to disappear.

Processes for brightening polyacrylonitrile fibres which are in the gel state essentially consist of bringing the fibres, in the swollen state, into contact with the brightener solution either on a padder or in a bath. The latter can for example also be effected by moving the fibre or the hank of fibres through a brightener solution or suspension flowing in counter-current. The baths to be used are appropriately prepared by dissolving or dispersing the brightener in water and adjusting the resulting liquor to the desired pH value with acid and/or a buffer salt. This pH value is generally between 1 and 7, and is, for example, 1.5 to 5.5. The concentration of brightener in the bath is in mostcases so chosen that after the treatment 0.005 to 0.5 percent, for example 0.05 to 0.2 percent, of brightener, relative to the dry weight of the fibre, is absorbed on the fibre. The treatment of the fibre in the brightener bath can be carried out at a bath temperature of below 50C, for example at l0 to 30C. In general, the duration of treatment of the fibre in the brightener bath is less than 2 minutes, preferably less than 40 seconds.

4 gory of derivatives of 4,4'-bis-[ l,3.5-triazinyl-(2)- amino]-sti|bene-2.2'-disulphonic acids show no significant effect.

EXAMPLE l A polyacrylonitrile tow obtained by the sodium thio cyanate wet spinning process. which has been rinsed and stretched but not dried. is immersed for 30 seconds into a solution of the following composition:

g/litre ot- 4,4'-bis (I-sulphostyrylMllphcnyl (solul ilit at 90C. approx. 260 g/l) 0.5 nil/litre of 98'; strength sulphuric acid pH of the solution: Temperature: Liquor ratio C 1 It) EXAMPLE 2 The experiments described in Example 1 are repeated, employing the compounds listed in Table l instead of 4,4'-bis-(2-sulphostyryl)-diphenyl. In this way, the degrees of whiteness indicated in Table l are obtained:

Table I Compound Solubility in water at C pH value of the bath Degree of whiteness of the fibre according to the ClBA whiteness scale 4,4'-Bis-( 3-sulphostyryl )-diphcnyl I80 150 I50 l90 l00 l00 l00 l00 approx. 50 g/l t0 g/l approx. 2 g/l MNLIIMLIINIJINMN The present invention also relates to the use of the brighteners of the formulae (1) to (10) for application onto polyacrylonitrile fibres which are in the gel state;

It is particularly surprising, in the present case, that the anionic brighteners of the indicated formulae give good effects whilst they fail when used for brightening polyacrylonitrile according to conventional methods (such as, for example, in the treatment of the previously stretched and dried fibre by the exhaustion process at 90C), that is to say are not absorbed on the fibrc, or are insufficiently absorbed to give a brightening which meets requirements.

A further surprising fact is that the anionic compounds of the indicated formulae are outstandingly suitable for the use according to the invention whilst, for example, anionic brighteners from the large cate- The last two experiments show that with this class of compound sufficient solubility in water is a prerequisite for achieving a satsifactory brightening effect.

EXAMPLE 3 t The experiments described in Example 1 are repeated, employing a compound of the formula (6), (8) or (9) instead of 4,4'-bis-(Z-sulphostyryl)-diphenyl.

60 The results thus obtained are listed in Table ll:

Compounds of pH Value Degree of whiteness the formula of the bath of the fibre according to the CIBA whiteness scalc EXAMPLE 4 Similar results to those in Examples 1 to 3 are obtained if, under otherwise identical conditions, the process is carried out in a continuous apparatus by the countercurrent principle, with the continuously added liquor introducing 1.0 g of one of the abovementioned compounds per minute into the bath and the throughput of polyacrylonitrile wet tow in the opposite direction being 400 g per minute (expressed as dry weight).

EXAMPLE 5 Similar brightening effects of those in Examples 1 to 4 are obtained by working in a static bath in which the concentration of one of the abovementioned compounds is kept constant at 0.1 g/litre whilst the fibre material is continuously drawn through the bath.

EXAMPLE 6 the gel state in a bath which contains at least one com- 7 pound of the formula SQsM V $03M wherein B is 4,4'-biphenylene, l,4-phenylene or 2,6- naphthylene, R is hydrogen, alkyl with l to 4 carbon atome, halogen, SO M or alkoxy with l to 4 carbon atoms located in the orthoor meta-position to the bridge member and M denotes the hydrogen, alkali metal, ammonium or amine salt ion, the solubility of these compounds in water at C being at least 10 g/l and drying the treated fibers.

2. A process according to claim 1 wherein B is 4-4- biphenylene.

3. A process according to claim 1 wherein the fibres are stretched prior to said treatment.

4. A process according to claim 1 wherein the fibres are stretched after said treatment.

5. A process according to claim 1 wherein the treatment of the fibres is carried out at a temperature below 50C.

6. A process according to claim 1 wherein the brightener concentration is so chosen that after the treatment 0.005 to 0.5 percent of brightener, relative to the dry weight of the fibres, has been applied to the fibres.

7. A process according to claim 1 wherein the duration of treatment of the fibres in the bath is less than 2 minutes.

8. A process according to claim 1 wherein the fibres are moved through the brightener liquor which is flowing in counter-current.

9. Polyacrylonitrile fibres which have been brightened according to the process of claim I. 

1. A PROCESS FOR PROVIDING BRIGHTENED POLYACRYLONITRILE STRETCHED FIBRES, COMPRISING TREATING THE FIBRES IN THE GEL STALE IN A BATH WHICH CONTAINS AT LEAST ONE COMPOUND OF THE FORMULA
 2. A process according to claim 1 wherein B is 4-4''-biphenylene.
 3. A process according to claim 1 wherein the fibres are stretched prior to said treatment.
 4. A process according to claim 1 wherein the fibres are stretched after said treatment.
 5. A process according to claim 1 wherein the treatment of the fibres is carried out at a temperature below 50*C.
 6. A process according to claim 1 wherein the brightener concentration is so chosen that after the treatment 0.005 to 0.5 percent of brightener, relative to the dry weight of the fibres, has been applied to the fibres.
 7. A process according to claim 1 wherein the duration of treatment of the fibres in the Bath is less than 2 minutes.
 8. A process according to claim 1 wherein the fibres are moved through the brightener liquor which is flowing in counter-current.
 9. Polyacrylonitrile fibres which have been brightened according to the process of claim
 1. 